Zirconia is best known among ceramics as being both hard and fracture-tough
at room temperature. Additionally, its fine (sub-micron)
grain size enables excellent surface finishes and the ability
to hold a sharp edge.

Although it retains many properties including corrosion resistance
at extremely high temperatures, zirconia does exhibit structural
changes that may limit its use to perhaps only 500 °C. It also
becomes electrically conductive as this temperature is approached.

Zirconia is commonly blended with either MgO, CaO, or Yttria as
a stabilizer in order to facilitate transformation toughening. This
induces a partial cubic crystal structure instead of fully tetragonal
during initial firing, which remains metastable during cooling.
Upon impact, the tetragonal precipitates undergo a stress induced
phase transformation near an advancing crack tip. This action expands
the structure as it absorbs a great deal of energy, and is the cause
of the high toughness of this material. Reforming also occurs dramatically
with elevated temperature and this negatively affects strength along
with 3-7% dimensional expansion. The amount of tetragonal can be
controlled by additions of the blends above to balance toughness
against loss of strength.

Cubic Zirconia: This single crystal optically clear form of ZrO2
has a relatively low fracture toughness and strength, but very high
thermal shock resistance.

Zirconia PSZ: Cream colored blends with approximately 10% MgO,
called partially stabilized zirconia (PSZ), are high in toughness,
and retain this property to elevated temperatures. They are somewhat
lower in cost but also have larger grain structure.

Zirconia TZP: Yttria blends of approximately 3% are called tetragonal
zirconia polycrystal (TZP) and have the finest grain size. These
grades exhibit the highest toughness at room temperature, because
they are nearly 100% tetragonal, but this degrades severely between
200 and 500°C as these irreversible crystal transformations also
cause dimensional change.

PROPERTY

UNITS

VALUE

REMARKS

Mechanical

Density

gm/cc

5.92

Hardness

Knoop

7.2

Tensile Strength

kpsi

-

Modulus
of Elasticity

psi
x 106

-

Young

Flexural
Strength

kpsi

-

Compressive Strength

kpsi

-

Poisson's
Ratio

-

-

Varies with Orientation

Fracture
Toughness

MPa
m1/2

-

Electrical

Dielectric
Strength

ac
volts/mil

-

Dielectric
Constant

(at 1 MHz)

-

parallel to the c-axis

Volume Resistivity

ohm-cm2/cm

-

-

Thermal

Coefficient of Thermal Expansion

x10-6/oC

8

parallel to the c-axis

Thermal
Conductivity

W/moK

31.8

-

Specific
Heat

cal/goC

-

-

Max
Working Temp

oC

2500

-

Shock
Resistance

oC diff.

Optical

Index
of Refraction

(Ordinary
ray, No,c-axis) (Extraordinary ray, Ne,c-axis)

2.1

-

-

-

Birefringence

(No-Ne)

-

-

Transmission
Band

Wavelength
of microns

-

All
properties are at room temperature unless otherwise noted.

Engineering data are representative, and are not intended
as absolute nor warrantable. Manufacturer'
s Data shown
is blended from multiple sources and therefore illustrates
the marketplace.